The present study investigates protective effects of Rosmarinus officinalis on oxidative stress and cardiac markers in isoproterenol (ISO)-induced myocardial infarction in rats. METHOD: Male albino wistar rats were divided into four groups (n=6). Group I received 0.5% CMC treated as normal control group. Group II received isoproterenol (85 mg/kg body weight .s.c) for two consecutive days (29th and 30th days). Group III received combination of Rosmarinus officinalis (100 mg/kg) intragastric intubation for 30 days. Group IV rats received combination of Rosmarinus officinalis as in Group III and additionally isoproterenol was given for two consecutive days (29th and 30th days). Induction of rats with ISO resulted in a well-marked elevation in lipid peroxidation and cardiac marker enzymes whereas, antioxidant activities were significantly reduced. Rosmarinus officinalis in resulted in significant reduction in lipid peroxidation and cardic marker enzymes. In addition, significant elevation of antioxidant activities was also observed in Rosmarinus officinalis in treated rats. When compared to the individual treatment groups. These findings conclude that Rosmarinus officinalis exhibited the protective effect of ISO induced myocardial infarction in rats.